Room-temperature vulcanisable organopolysiloxane compound to give an elastomer and novel organopolysiloxane polycondensation catalysts

ABSTRACT

The present invention relates to an organopolysiloxane composition that can be vulcanized at room temperature into an elastomer that is crosslinked by polycondensation and that does not contain alkyltin-based catalysts and also to novel organopolysiloxane polycondensation catalysts.

The present invention relates to an organopolysiloxane composition thatcan be vulcanized at room temperature into an elastomer that iscrosslinked by polycondensation and that does not contain alkyltin-basedcatalysts which exhibit toxicity problems.

The invention also relates to novel polycondensation catalysts insilicone chemistry, and to the uses thereof as catalysts for thepolycondensation reaction of organopolysiloxanes.

Elastomer formulations that crosslink via polycondensation generallyinvolve a silicone oil, generally a polydimethylsiloxane, with hydroxylend groups, optionally prefunctionalized by a silane so as to havealkoxy ends, a crosslinker, a polycondensation catalyst, conventionallya tin salt or an alkyl titanate, a reinforcing filler and other optionaladditives such as bulking fillers, adhesion promoters, colorants,biocidal agents, etc.

These room-temperature vulcanizing organopolysiloxane compositions arewell known and are classified into 2 different groups: single-componentcompositions (RTV-2) and two-component compositions (RTV-1).

During crosslinking, water (either provided by atmospheric moisture inthe case of RTV-1 compositions, or introduced into one part of thecomposition in the case of RTV-2 compositions) enables thepolycondensation reaction, which results in the formation of theelastomeric network.

Generally, single-component (RTV-1) compositions crosslink when they areexposed to moisture from the air, that is to say that they cannotcrosslink in an enclosed medium. For example, the single-componentsilicone compositions used as sealants or cold-setting adhesives followa mechanism of hydrolysis of reactive functional groups of theacetoxysilane, ketiminoxysilane, alkoxysilane, etc. type, followed bycondensation reactions between the silanol groups formed and otherresidual reactive functional groups. The hydrolysis is generally carriedout by virtue of water vapor which diffuses into the material from thesurface exposed to the atmosphere. Generally, the kinetics of thepolycondensation reactions is extremely slow; these reactions aretherefore catalyzed by a suitable catalyst. As catalysts which are used,use is most often made of catalysts based on tin, titanium, an amine orcompositions of these catalysts. Catalysts based on tin (cf. inparticular FR-A-2 557 582) and on titanium in particular FR-A-2 786 497)are catalysts that are very effective.

As regards two-component compositions, they are sold and stored in theform of two components, a first component containing the base polymermaterials and the second component containing the catalyst. The twocomponents are mixed at the moment of use and the mixture crosslinks inthe form of a relatively hard elastomer. These two-componentcompositions are well known and are described, in particular, in thebook by Walter Noll “Chemistry and Technology of Silicones” 1968, 2ndEdition, on pages 395 to 398. These compositions essentially comprise 4different ingredients:

-   -   a reactive α,ω-dihydroxydiorganopolysiloxane polymer,    -   a crosslinking agent, generally a silicate or a polysilicate,    -   a tin catalyst, and    -   water.

Usually, the condensation catalyst is based on an organic tin compound.Indeed, many tin-based catalysts have already been proposed ascrosslinking catalysts for these RTV-2 compositions. The most widelyused compounds are alkyltin carboxylates such as tributyltin monooleateor dialkyltin dicarboxylates such as dibutyltin dilaurate, dibutyltindiacetate or dimethyltin dilaurate (see the book by Noll “Chemistry andTechnology of silicones” page 337, Academic Press, 1968—2^(nd) Editionor patents EP 147 323 or EP 235 049).

However, the alkyltin-based catalysts, although very effective, usuallycolorless, liquid and soluble in silicone oils, have the drawback ofbeing toxic (CMR2 toxic for reproduction).

Titanium-based catalysts, also widely used in RTV-1 compositions, havehowever a major drawback: they have slower kinetics than tin-basedcatalysts. Furthermore, these catalysts cannot be used in RTV-2compositions due to gelling problems.

Other catalysts are sometimes mentioned, such as catalysts based onzinc, zirconium or aluminum, but they have only experienced minorindustrial development due to their mediocre effectiveness.

Coatings formed from alkoxysilanes (component (A)) optionally in thepresence of a metal alcoholate (component (E)), in particular ceriumalcoholates, have also been described in the reference WO 2006/041445,see page 36, lines 18 to 35. Alkoxysilanes are well known for their highreactivity and their ability to crosslink, even without the presence ofcatalyst. It is clearly indicated on page 29, line 17 that these metalalcoholates are optionally used as catalysts for the alkoxysilane. Thisreference does not describe crosslinkable compositions that compriseorganopolysiloxanes.

For sustainable development, it therefore appears necessary to developnontoxic catalysts for the polycondensation reaction oforganopolysiloxanes.

Another important aspect for a catalyst of the polycondensation reactionof organopolysiloxanes is the pot life, that is to say the time duringwhich the composition can be used after mixing without curing. This timemust be long enough to allow it to be used, but short enough to obtain amoulded article that can be handled at the latest a few minutes or a fewhours after it has been manufactured. The catalyst must thus make itpossible to obtain a good compromise between the pot life of thecatalyzed mixture and the time at the end of which the molded articlecan be handled (these times depend on the targeted application such as,for example, the molding or manufacture of seals). In addition, thecatalyst must confer, on the catalyzed mixture, a spreading time whichdoes not vary as a function of the storage time.

The main objective of the present invention is therefore to find acatalyst that can be used both in the crosslinking of single-componentand two-component elastomer compositions.

Another main objective of the present invention is to propose a catalystsystem that continues to simultaneously meet the constraints of storage,of processing and of crosslinking of the two types of single-componentand two-component elastomer compositions.

Another main objective of the present invention is to propose a catalystsystem that continues to simultaneously meet the constraints of storage,of processing and of crosslinking of the two types of single-componentand two-component elastomer compositions.

An organopolysiloxane composition has now been found, and it is thiswhich constitutes the subject of the present invention, characterized inthat the organopolysiloxane composition comprises:

-   -   a silicone base B capable of curing via polycondensation        reaction into a silicone elastomer, said silicone base        comprising:        -   at least one polyorganosiloxane oil C capable of            crosslinking via polycondensation into an elastomer;        -   optionally at least one crosslinking agent D;        -   optionally at least one adhesion promoter E; and        -   optionally at least one siliceous, organic and/or            non-siliceous mineral filler F; and    -   a catalytically effective amount of at least one        polycondensation catalyst which is a metal complex or salt A of        formula (1) below:

[M(L¹)_(r1)(L²)_(r2)(Y)_(x)]  (1)

-   -   in which:        -   r1≧1, r2≧0 and x≧0;        -   the symbol M represents a metal selected from the group            constituted by: cerium, bismuth and molybdenum;        -   the symbol L¹ represents a ligand which is an alcoholate            anion and when r1≧2, the symbols L¹ are identical or            different;        -   the symbol L² represents an anionic ligand which is            different from L¹ and when r2≧2, the symbols L² are            identical or different; and        -   the symbol Y represents a neutral ligand and when x≧2, the            symbols Y are identical or different.

It is understood that the definition of “metal complex or salt A offormula (1)” includes any oligomeric form or analog of said metalcomplex or salt A.

It is to the credit of the inventors that they have found, quitesurprisingly and unexpectedly, that it is advisable to use metalcomplexes of a selection of certain metals, at least one ligand of whichis an alcoholate anion, in order to obtain excellent catalyst for thepolycondensation reaction of organopolysiloxanes.

It is also to the credit of the inventors that they have overcome thetechnical prejudice that hitherto decreed that certain complexes ofmetals having an alcoholate ligand have only a mediocre activity in thepolycondensation reaction of organopolysiloxanes, or even nocrosslinking action (FR-1 423 477, page 2).

The definition of the ligands is taken from the book “ChimieOrganométallique” [Organometallic Chemistry] by Didier Astruc, publishedin 2000 by EDP Sciences, cf., in particular, Chapter 1, “Les complexesmonométalliques” [Single metal complexes], pages 31 et seq.

The nature of the neutral ligand Y is not very important and a personskilled in the art will use any type of neutral ligand suitable for themetal in question.

The catalyst according to the invention may be in the solid or liquidstate. It may be incorporated alone or in a suitable solvent. When it isin solvent, a silicone oil may be added, the solvent is then evaporatedso as to transfer the catalyst into a silicone medium. The mixtureobtain acts as a catalyzing base.

According to one preferred embodiment, the polycondensation catalystaccording to the invention is a metal complex or salt A of formula (1′)below:

[M(L¹)_(r1)(L²)_(r2)]  (1′)

in which:

-   -   r1≧1 and r2≧0;    -   the symbol M represents a metal selected from the group        constituted by: cerium, bismuth and molybdenum;    -   the symbol L¹ represents a ligand which is an alcoholate anion        and when r1≧2, the symbols L¹ are identical or different; and    -   the symbol L² represents an anionic ligand which is different        from L¹ and when r2≧2, the symbols L² are identical or        different.

According to another preferred embodiment, the polycondensation catalystaccording to the invention is a metal complex or salt A chosen from thegroup constituted by the complexes of formulae (2) to (4) below:

[Ce(L¹)_(r3)(L²)_(r4)];where r3≧1 and r4≧0 and r3+r4=3;  (2)

[Mo(L¹)_(r5)(L²)_(r6)];where r5≧1 and r6≧0 and r5+r6=6;  (3)

[Bi(L¹)_(r7)(L²)_(r8)];where r7≧1 and r8≧0 and r7+r8=3;  (4)

in which:

-   -   the symbol L¹ represents a ligand which is an alcoholate anion        and when the number of ligands L¹≧2, the symbols L¹ possibly        being identical or different; and    -   the symbol L² represents an anionic ligand which is different        from L¹ and when the number of ligands L²≧2, the symbols L²        possibly being identical or different.

For carrying out the invention use is preferably made, aspolycondensation catalyst according to the invention, of a metal complexor salt A chosen from the group constituted by the complexes (5) to (14)below:

[Ce(OiPr)₄]where(OiPr)=the isopropylate anion;  (5)

[Mo(O₂)(2,3-butanediolate)₂];  (7)

[Mo(O₂)(ethylene glycolate)₂];  (8)

[Mo(O₂)(1,2-propanediolate)₂];  (9)

[Mo(O₂)(pinanediolate)₂];  (10)

[Mo(O₂)(1,3-propanediolate)];  (11)

[Mo(O₂)(meso-2,3-butanediolate)₂];  (12)

[Mo(O₂)(1,2-octanediolate)₂];and  (13)

[Bi(monoallyl ethylene glycolate)₃].  (14)

It should be noted that at least one part of the inventive nature of theinvention is due to the judicious and advantageous selection of thedefined associations of metal complexes or salts A used aspolycondensation catalyst.

According to one preferred embodiment of the invention, the symbol L¹represents a ligand which is an alcoholate anion chosen from the groupconstituted by the alcoholate anions derived from the followingalcohols: methanol, ethanol, propanol, isopropanol, n-butanol,cyclopentanol, cycloheptanol, cyclohexanol, s-butanol, t-butanol,pentanol, hexanol, octanol, decanol, isopropyl alcohol, allyl alcohol,diols such as, for example, ethylene glycol, 1,2-propanediol,pinanediol, 1,3-propanediol and 1,2-octanediol, 1,2-cyclohexanediol and2,3-butanediol.

In order to explain in a little more detail the nature of theconstituent elements of the metal complex A according to the invention,it is important to specify that L² is an anionic ligand which may beselected from the group constituted by the following anions: fluoro(F⁻), chloro (Cl⁻), triiodo (1⁻) (I₃)⁻, difluorochlorato (1⁻) [ClF₂]⁻,hexafluoroiodato (1⁻) [IF₆]⁻, oxochlorato (1⁻) (CIO)⁻, dioxochlorato(1⁻) (CIO₂)⁻, trioxochlorato (1⁻) (CIO₃)⁻, tetraoxochlorato (1⁻)(CIO₄)⁻, hydroxo (OH)⁻, mercapto (SH)⁻, selanido (SeH)⁻, hyperoxo (O₂)⁻,ozonido (O₃)⁻, hydroxo (OH⁻), hydrodisulfido (HS₂)⁻, methoxo (CH₃O)⁻,ethoxo (C₂H₅O)⁻, propoxido (C₃H₇O)⁻, methylthio (CH₃S)⁻, ethanethiolato(C₂H₅S)⁻, 2-chloroethanolato (C₂H₄CIO)⁻, phenoxido (C₆H₅O)⁻, phenylthio(C₆H₅S)⁻, 4-nitrophenolato [C₆H₄(NO₂)O]⁻, formato (HCO₂)⁻, acetato(CH₃CO₂)⁻, propionato (CH₃CH₂CO₂)⁻, nitrido (N₃)⁻, cyano (CN)⁻, cyanato(NCO)⁻, thiocyanato (NCS)⁻, selenocyanato (NCSe)⁻, amido (NH₂)⁻,phosphino (PH₂)⁻, chloroazanido (ClHN)⁻, dichloroazanido (Cl₂N)⁻,[methanaminato (1⁻)] (CH₃NH)⁻, diazenido (HN═N)⁻, diazanido (H₂N—NH)⁻,diphosphenido (HP═P)⁻, phosphonito (H₂PO)⁻, phosphinato (H₂PO₂)⁻,carboxylato, enolato, amides, alkylato and arylato.

According to one particularly preferred embodiment, L² is an anionicligand selected from the group constituted by the following anions:acetate, propionate, butyrate, isobutyrate, diethylacetate, benzoate,2-ethylhexanoate, stearate, methoxide, ethoxide, isopropoxide,tert-butoxide, tert-pentoxide, 8-hydroxyquinolinate, naphthenate,tropolonate and the oxido O²⁻ anion.

The nature of the neutral ligand Y is not very important and a personskilled in the art will use any type of neutral ligand suitable for themetal in question.

Another subject of the invention consists of the use, as a catalyst forthe polycondensation reaction of organopolysiloxanes, of metal complexesor salts A according to the invention as described above.

Another subject of the invention consists of the use, as a catalyst forthe polycondensation reaction, of the compounds chosen from the groupconstituted by the complexes of formulae (5) to (14):

[Ce(OiPr)₄]where(OiPr)=the isopropylate anion;  (5)

[Mo(O₂)(2,3-butanediolate)₂];  (7)

[Mo(O₂)(ethylene glycolate)₂];  (8)

[Mo(O₂)(1,2-propanediolate)₂];  (9)

[Mo(OH)(pinanediolate)₂];  (10)

[Mo(O₂)(1,3-propanediolate)₂];  (11)

[Mo(O₂)(meso-2,3-butanediolate)₂];  (12)

[Mo(O₂)(1,2-octanediolate)₂];and  (13)

[Bi(monoallyl ethylene glycolate)₃].  (14)

According to another of its aspects, one subject of the presentinvention is also the novel compounds of the following formulae:

[Mo(O₂)(pinanediolate)₂];and  (10)

[Bi(monoallyl ethylene glycolate)₃].  (14)

The amount of polycondensation catalyst according to the invention(metal complex or salt A) is between 0.1 and 10% by weight of the totalweight, preferably between 0.5 and 5%, whether it is a single-componentor two-component preparation.

Description of the Silicone Base B:

The silicone bases used in the present invention that crosslink and curevia polycondensation reactions are well known. These bases are describedin detail in particular in numerous patents and they are commerciallyavailable.

These silicone bases may be single-component bases, that is to say basesthat are packaged in a single package, and stable during storage, in theabsence of moisture, which can be cured in the presence of moisture, inparticular moisture provided by the ambient air or by water generatedwithin the base during the use thereof.

Apart from single-component bases, use may be made of two-componentbases, that is to say bases that are packaged in two packages, whichcure as soon as the catalyst according to the invention is incorporated.They are packaged, after incorporation of the catalyst, in two separatefractions, one of the fractions possibly containing, for example, onlythe catalyst according to the invention or a mixture with thecrosslinking agent.

The silicone base B used to produce the composition according to theinvention may comprise:

-   -   at least one polyorganosiloxane oil C capable of crosslinking        via polycondensation into an elastomer;    -   optionally at least one crosslinking agent D;    -   optionally at least one adhesion promoter E; and    -   optionally at least one siliceous, organic and/or non-siliceous        mineral filler F.

The polyorganosiloxane oil C is preferably anα,ω-dihydroxypolydiorganosiloxane polymer, with a viscosity between 50and 5 000 000 mPa·s at 25° C. and the crosslinking agent D is preferablyan organosilicon compound bearing more than two hydrolyzable groupsbonded to the silicon atoms per molecule. The polyorganosiloxane oil Cmay also be functionalized at its ends by hydrolyzable radicals obtainedby condensation of a precursor bearing hydroxyl functional groups with acrosslinking silane bearing hydrolyzable radicals.

As the crosslinking agent (D), mention may be made of:

-   -   silanes of the following general formula:

R¹ _(k)Si(OR²)_((4-k))

in which the symbols R², which are identical or different, representalkyl radicals having from 1 to 8 carbon atoms, such as methyl, ethyl,propyl, butyl, pentyl or 2-ethylhexyl radicals, C₃-C₆ oxyalkyleneradicals, the symbol R¹ represents a linear or branched, saturated orunsaturated, aliphatic hydrocarbon-based group, a saturated orunsaturated and/or aromatic, monocyclic or polycyclic carbocyclic group,and k is equal to 0, 1 or 2; and

-   -   the partial hydrolysis products of this silane.

As examples of C₃-C₆ alkoxyalkylene radicals, mention may be made of thefollowing radicals:

-   CH₃OCH₂CH₂—-   —CH₃OCH₂CH(CH₃)—-   —CH₃OCH(CH₃)CH₂—-   —C₂H₅OCH₂CH₂CH₂—

The symbol R¹ represents a C₁-C₁₀ hydrocarbon-based radical thatencompasses:

-   -   C₁-C₁₀ alkyl radicals such as methyl, ethyl, propyl, butyl,        pentyl, 2-ethylhexyl, octyl or decyl radicals;    -   vinyl and allyl radicals; and    -   C₅-C₈ cycloalkyl radicals such as phenyl, tolyl and xylyl        radicals.

The crosslinking agents D are products that are available on thesilicones market; furthermore, their use in room-temperature curingcompositions is known; it occurs in particular in French patents FR-A-1126 411, FR-A-1 179 969, FR-A-1 189 216, FR-A-1 198 749, FR-A-1 248 826,FR-A-1 314 649, FR-A-1 423 477, FR-A-1 432 799 and FR-A-2 067 636.

Preference is more particularly given, among the crosslinking agents D,to alkyltrialkoxysilanes, alkyl silicates and alkyl polysilicates, inwhich the organic radicals are alkyl radicals having from 1 to 4 carbonatoms.

As other examples of crosslinking agents D that may be used, mention ismore particularly made of the following silanes:

-   propyltrimethoxysilane;-   methyltrimethoxysilane;-   ethyltrimethoxysilane;-   vinyltriethoxysilane;-   methyltriethoxysilane;-   vinyltriethoxysilane;-   propyltriethoxysilane;-   tetraethoxysilane;-   tetrapropoxysilane;-   1,2-bis(trimethoxysilyl)ethane;-   1,2-bis(triethoxysilyl)ethane; and-   tetraisopropoxysilane,-   or else: CH₃Si(OCH₃)₃; C₂H₅Si(OC₂H₅)₃; C₂H₅Si(OCH₃)₃CH₂═CHSi(OCH₃)₃;    CH₂═CHSi(OCH₂CH₂OCH₃)₃C₆H₅Si(OCH₃)₃;    [CH₃][OCH(CH₃)CH₂OCH₃]Si[OCH₃]₂Si(OCH₃)₄; Si(OC₂H₅)₄;    Si(OCH₂CH₂CH₃)₄; Si(OCH₂CH₂CH₂CH₃)₄Si(OC₂H₄OCH₃)₄;    CH₃Si(OC₂H₄OCH₃)₃; CICH₂Si(OC₂H₅)_(3.)

As other examples of crosslinking agent D, men on may be made of ethylpolysilicate or n-propyl polysilicate.

Use is generally made of 0.1 to 60 parts by weight of crosslinking agentD per 100 parts by weight of polyorganosiloxane C capable ofcrosslinking via polycondensation to an elastomer.

Thus the composition according to the invention may comprise at leastone adhesion promoter E such as, for example, the organosiliconcompounds bearing both:

-   -   (1) one or more hydrolyzable groups bonded to the silicon atom,        and    -   (2) one or more organic groups substituted with radicals        comprising a nitrogen atom or chosen from the group of        (meth)acrylate, epoxy and alkenyl radicals, and more preferably        still from the group constituted by the following compounds,        taken alone or as a mixture:

-   vinyltrimethoxysilane (VTMO);

-   3-glycidoxypropyltrimethoxysilane (GLYMO);

-   methacryloxypropyltrimethoxysilane (MEMO);

-   [H₂N(CH₂)₃]Si(OCH₂CH₂CH₃)₃;

-   [H₂N(CH₂)₃]Si(OCH₃)₃;

-   [H₂N(CH₂)₃]Si(OC₂H₅)₃;

-   [H₂N(CH₂)₄]Si(OCH₃)₃;

-   [H₂NCH₂CH(CH₃)CH₂CH₂]SiCH₃(OCH₃)₂;

-   [H₂NCH₂]Si(OCH₃)₃;

-   [n-C₄H₉—HN—CH₂]Si(OCH₃)₃;

-   [H₂N(CH₂)₂NH(CH₂)₃]Si(OCH₃)₃;

-   [H₂N(CH₂)₂NH(CH₂)₃]Si(OCH₂CH₂OCH₃)₃;

-   [CH₃NH(CH₂)₂NH(CH₂)₃]Si(OCH₃)₃;

-   [H(NHCH₂CH₂)₂NH(CH₂)₃]Si(OCH₃)₃;

or polyorganosiloxane oligomers containing such organic groups at acontent greater than 20%.

For the single-component and two-component bases, use is made, as themineral fillers F, of very finely divided products, the average particlediameter of which is less than 0.1 μm. These fillers include fumedsilicas and precipitated silicas; their BET specific surface area isgenerally greater than 40 m²/g. These fillers may also be in the form ofmore coarsely divided products, having an average particle diametergreater than 0.1 μm. As examples of such tillers, mention may be made ofground quartz, diatomaceous silicas, calcium carbonate, calcined clay,rutile-type titanium oxide, iron, zinc, chromium, zirconium or magnesiumoxides, the various forms of alumina (hydrated or unhydrated), boronnitride, lithopone, barium metaborate, barium sulfate and glassmicrobeads; their specific surface area is generally less than 30 m²/g.

These fillers may have been surface-modified by treatment with thevarious organosilicon compounds customarily employed for this purpose.Thus, these organosilicon compounds may be organochlorosilanes,diorganocyclopolysiloxanes, hexaorganodisiloxanes, hexaorganodisilazanesor diorganocyclopolysilazanes (French patents FR-A-1 126 884, FR-A-1 136885 and FR-A-1 236 505, and British patent GB-A-1 024 234). The treatedfillers contain, in most cases, from 3 to 30% of their weight oforganosilicon compounds. The fillers may be constituted of a mixture ofseveral types of fillers of different particle size; thus, for example,they may be constituted of 30 to 70% of finely divided silicas with aBET specific surface area greater than 40 m²/g and of 70 to 30% of morecoarsely divided silicas with a specific surface area less than 30 m²/g.

The purpose of introducing fillers is to give good mechanical andrheological properties to the elastomers that result from the curing ofthe compositions according to the invention.

In combination with these fillers, use may be made of mineral and/ororganic pigments and also agents that improve the thermal resistance(salts and oxides of rare-earth elements such as ceric oxides andhydroxides) and/or the fire resistance of the elastomers. For example,it is possible to use the cocktails of oxides described in internationalapplication WO 98/29488. Mention may be made, among the agents forimproving the fire resistance, of halogenated organic derivatives,organic phosphorus derivatives, platinum derivatives, such aschloroplatinic acid (its reaction products with alkanols or ethers), orplatinous chloride-olefin complexes. These pigments and agents togetherrepresent at most 20% of the weight of the fillers.

Other customary auxiliary agents and additives may be incorporated intothe composition according to the invention, these are chosen as afunction of the applications in which said compositions are used.

The silicone base used to produce the composition according to theinvention may comprise:

-   -   100 parts of polyorganosiloxane oil C capable of crosslinking        via polycondensation into an elastomer;    -   0 to 20 parts of a crosslinking agent D;    -   0 to 20 parts of an adhesion promoter E; and    -   0 to 50 parts of filler F.

In addition to the main constituents, nonreactive linearpolyorganosiloxane polymers G may be introduced with the intention ofacting on the physical characteristics of the compositions in accordancewith the invention and/or on the mechanical properties of the elastomersresulting from the curing of these compositions.

These nonreactive linear polyorganosiloxane polymers G are well known;they comprise more especially:α,ω-bis(triorganosiloxy)diorganopolysiloxane polymers with viscositiesof at least 10 mPa·s at 25° C. formed essentially of diorganosiloxyunits and of at least 1% of monoorganosiloxy and/or siloxy units, theorganic radicals bonded to the silicon atoms being chosen from themethyl, vinyl and phenyl radicals, 60% at least of these organicradicals being methyl radicals and 10% at most being vinyl radicals. Theviscosity of these polymers can reach several tens of millions of mPa·sat 25° C.; they therefore include oils with a fluid to viscousappearance and soft to hard gums. They are prepared according to theusual techniques described more specifically in French patents FR-A-978058, FR-A-1 025 150, FR-A-1 108 764 and FR-A-1 370 884. Use ispreferably made of α,ω-bis(trimethylsiloxy)dimethylpolysiloxane oilswith a viscosity ranging from 10 mPa·s to 1000 mPa·s at 25° C. Thesepolymers, which act as plasticizers, can be introduced in a proportionof at most 70 parts, preferably of 5 to 20 parts, per 100 parts of thepolyorganosiloxane oil C capable of crosslinking via polycondensation.

The compositions according to the invention can in additionadvantageously comprise at least one silicone resin H. These siliconeresins are branched organopolysiloxane polymers which are well known andwhich are available commercially. They have, per molecule, at least twodifferent units chosen from those of formula R′″₃SiO_(1/2) (M unit),R′″₂SiO_(2/2) (D unit), R′″SiO_(3/2)(T unit) and SiO_(4/2) (Q unit). TheR′″ radicals are identical or different and are chosen from linear orbranched alkyl radicals or vinyl, phenyl or 3,3,3-trifluoropropylradicals. Preferably, the alkyl radicals have from 1 to 6 carbon atomsinclusive. More particularly, mention may be made, as alkyl R radicals,of methyl, ethyl, isopropyl, tert-butyl and n-hexyl radicals. Theseresins are preferably hydroxylated and have, in this case, a weightcontent of hydroxyl groups of between 5 and 500 meq/100 g.

Mention may be made, as examples of resins, of MQ resins, MDQ resins, TDresins and MDT resins.

In order to manufacture the compositions according to the invention itis necessary, in the case of the single-component compositions, to useequipment that makes it possible to intimately mix the variousfundamental constituents in a moisture-free environment, with or withouta supply of heat, optionally added to which constituents are theaforementioned adjuvants and additives. All these ingredients may beloaded into the equipment in any order of introduction. Thus, it ispossible to firstly mix the organopolysiloxane oils C and the fillers Fand then to add to the paste obtained the crosslinkers D, the compoundsE and the catalyst according to the invention. It is also possible tomix the oils C, the crosslinkers D, the compounds E and the fillers Fand to subsequently add the catalyst according to the invention. Duringthese operations, the mixtures may be heated at a temperature within therange of 50-180° C. under atmospheric pressure or under a reducedpressure in order to promote the removal of volatile materials.

The single-component compositions according to the invention, used asthey are, that is to say undiluted, or in the form of dispersions indiluents, are stable during storage in the absence of water and cure atlow temperatures (after removal of solvents in the case of dispersions)in the presence of water to form elastomers.

After the deposition of the compositions as they are, onto solidsubstrates, in a humid atmosphere, it is observed that a process ofcuring into elastomers occurs, it takes place from the outside to theinside of the mass deposited. A skin forms first at the surface, thenthe crosslinking continues in depth. The complete formation of the skin,which results in a tack-free feel of the surface, requires a period oftime of a few minutes; this period of time depends on the degree ofrelative humidity of the atmosphere surrounding the compositions and onthe crosslinkability of the latter.

Furthermore, the in-depth curing of the deposited layers, which must besufficient to allow the demolding and handling of the elastomers formed,requires a longer period of time. Indeed, this period of time dependsnot only on the factors mentioned above for the formation of thetack-free feel but also on the thickness of the deposited layers, whichthickness generally lies between 0.5 mm and several centimeters. Thesingle-component compositions may be used for multiple applications suchas jointing in the construction industry, assembling the most diversematerials (metals, plastics, natural and synthetic rubbers, wood, board,earthenware, brick, ceramic, glass, stone, concrete, masonry units),insulating electrical conductors, the potting of electronic circuits, orthe preparation of molds used for manufacturing articles made ofsynthetic resins or foams.

The manufacture of the two-component compositions according to theinvention is also carried out by mixing various constituents in suitableequipment. In order to obtain homogeneous compositions, it is preferableto firstly mix the polymers A with the fillers C; the whole mixture maybe heated for at least 30 minutes at a temperature above 80° C., so asto complete the wetting of the fillers by the oils. To the mixtureobtained, preferably brought to a temperature below 80° C., for exampleof around room temperature, may be added the other constituents, that isto say the crosslinking agents, the catalyst and optionally variousadditives and adjuvants and even water.

The compositions in accordance with the invention may be employed formultiple applications, such as jointing and/or bonding in theconstruction industry or the transportation industry (e.g.: automobile,aerospace, railroad, maritime and aeronautical industries), assemblingthe most diverse materials (metals, plastics, natural and syntheticrubbers, wood, boards, polycarbonate, earthenware, brick, ceramic,glass, stone, concrete and masonry units), insulating electricalconductors, the potting of electronic circuits, and the preparation ofmolds used for manufacturing articles made of synthetic resins or foams.

Thus, another subject of the invention consists of a two-componentsystem that is a precursor of the organopolysiloxane compositionaccording to the invention and as defined above and that can bevulcanized to a silicone elastomer via polycondensation reactions andcharacterized in that it is in two separate parts P1 and P2 intended tobe mixed in order to form said composition, and in that one of theseparts comprises the metal complex or salt A according to the inventionand as defined above as a catalyst for the polycondensation reaction oforganopolysiloxanes and the crosslinking agent D, whilst the other partis free of the aforementioned species and comprises:

-   -   per 100 parts by weight of the polyorganosiloxane oil(s) C        capable of crosslinking via polycondensation into an elastomer;    -   from 0.001 to 10 part(s) by weight of water.

Another subject of the invention also consists of a single-componentpolyorganosiloxane composition that is stable during storage in theabsence of moisture and that crosslinks, in the presence of water, intoan elastomer, characterized in that it comprises:

-   -   at least one crosslinkable linear polyorganopolysiloxane that        has functionalized ends of alkoxy, oxime, acyl and/or enoxy        type, preferably alkoxy type;    -   a filler; and    -   a catalyst of the polycondensation reaction which is the metal        complex A according to the invention and as defined above.

Single-component bases are described in detail, for example, in patentsEP 141 685, EP 147 323, EP 102 268, EP 21 859, FR 2 121 289 and FR 2 121631, cited as reference.

It possible to add, to these single-component bases, adhesion promotersE chosen, for example, from organosilicon compounds simultaneouslybearing, on the one hand, organic groups substituted by radicals chosenfrom the group of amino, ureido, isocyanate, epoxy, alkenyl,isocyanurate, hydantoyl, guanidino and mercaptoester radicals and, onthe other hand, hydrolyzable groups, in general alkoxy groups bonded tothe silicon atoms. Examples of such adhesion agents are described inU.S. Pat. No. 3,517,001, U.S. Pat. No. 4,115,356, U.S. Pat. No.4,180,642, U.S. Pat. No. 4,273,698, U.S. Pat. No. 4,356,116 and inEuropean patents EP 31 996 and EP 74 001.

Two-component bases are described in detail, for example, in patents EP118 325, EP 117 772, EP 10 478, EP 50 358, EP 184 966, U.S. Pat. No.3,801,572 and U.S. Pat. No. 3,888,815 cited as reference.

Another subject of the invention consists of the use of a metal complexor salt A according to the invention and as defined above as a catalystfor the polycondensation reaction of organopolysiloxanes.

The final subject of the invention consists of an elastomer obtained bycrosslinking and curing of the two-component system according to theinvention and as described above, or of the composition according to theinvention and as described above.

Other advantages and features of the present invention will appear onreading the following examples that are given by way of illustration andthat are in no way limiting.

EXAMPLES Example 1 Catalyst Synthesis

Synthesis of Catalyst (10): [Mo(O₂)(pinanediolate)₂]

Added to a suspension of 4 mmol of molybdenyl acetylacetonate (1.2 g) in20 ml of cyclohexane were 16 mmol of pinanediol (2.72 g), then themixture was heated at reflux. After 1 h 30 min, the medium turned aclear orange color, then formed a bright yellow solid. After 3 h 30 min,the mixture was concentrated and the solid obtained was recrystallizedin cyclohexane to give 1.5 g of bright yellow solid of molybdenylpinanediolate in the form of its dehydrated dimer[MoOH(pinanediolate)₂]₂O based on the characteristic IR bands at 751 nm(according to Sheldon. Recl. Tray. Chim. Pays Bas, 92, 253 (1973)).

Mo calc. 20.97%, found (ICP) 16.0% (the product contains pinanediol)

Synthesis of Catalyst (14): [Bi(monoallyl ethylene glycolate)₃]

Added over 15 min to a suspension of 48 mmol of sodium hydride (2 g at60% previously washed with pentane) in 50 ml of anhydrous THF were 48mmol of ethylene glycol monoallyl ether (5.31 g). The solution obtainedwas added over 10 min to a solution of 16 mmol of bismuth trichloride(5.04 g) in 100 ml of the same solvent. After stirring for 4 h at roomtemperature, the homogeneous brown solution was evaporated to dryness.The brown solid was taken up with hexane, and the mixture filtered overcelite. After evaporation of the solvent, a brown liquid was obtained(5.2 g).

Bi calc. 40.78%, found (ICP) 32.5% (the product isolated containsethylene glycol monoallyl ether)

IR: 2844, 1347, 1066, 993, 918.

Example 2 Initial Test

In order to demonstrate the catalytic activity of novel molecules, twosimple tests were developed:

In the 2 tests, the procedure below was followed:

-   -   The functionalized or unfunctionalized oil, then the catalyst,        then the crosslinker in the case of the RTV2 composition, then        optionally the water were placed successively in a small open        cylindrical container equipped with a magnetic stirrer bar, and        the stirring was set at 300 rpm. The following were measured:        the time when the stirring stops which corresponds to a        viscosity of 1000 cP (or mPa) approximately, then the time for        the oil to no longer flow, the tack-free skin-over time and the        core crosslinking time. The activity of novel catalysts was        compared to that of tetrabutyldistannoxane dilaurate or Tegokat        225, one of the fastest dialkyltin type catalysts (1.24 mmol in        Sn equivalents).

RTV2 Test:

The species to be tested was brought into contact with a shortα,ω-dihydroxylated polydimethylsiloxane oil (½ equivalent relative tothe OH content, viscosity of 100 mPa·s. 48V100 oil) then a crosslinker,ethyl silicate was added (1 equivalent/OH), or the same volume of“advanced” ethyl silicate, that is to say a mixture ofethoxypolysiloxanes (in this case >1 eq/OH).

The amounts used in the examples below, unless mentioned, were thefollowing:

-   -   4.48 g of 48V100 oil having 0.553 mmol OH/g (viscosity: 100 cP        or mPa);    -   1.24 mmol of species to be tested (½ eq./OH);    -   0.52 g of ethyl silicate (1 eq./OH) in the presence or absence        of 90 μl of water (2 eq./OH), or the same volume of “advanced”        silicate as the ethyl silicate (=0.82 g).

RTV1 Test:

The same oil used before was previously functionalized withvinyltrimethoxysilane (VTMO); the species to be tested was brought intocontact with this oil under the same conditions as before, then 2equivalents of water were added (2 eq./initial OH).

The amounts used in the examples below, unless mentioned, were thefollowing:

-   -   4.77 g of VTMO-functionalized 48V100 oil;    -   1.24 mmol of species to be tested (½ eq./OH);    -   90 μl of water (added after 1 min of stirring=t₀).        The results of the RTV1 test are given in table I below:

TABLE I RTV1 tests Time when Time to end Tack-free Crosslinking stirringstops of flowability time time Hard/soft Test No. Metal Catalyst (h:min)(h:min) (h:min) (h:min) after 24 h Comparative Sn Tegokat225 00:19 00:2200:25 00:34 hard example 1 Bi Bi(ethylene glycolate 00:42 00:42 00:5001:00 hard monoallyl ether)₃ 2 Ce Ce(OiPr)4 00:12 01:40 00:40 02:30 hard3 Mo MoO₂(ethylene between 8 between 8 between 8 between 8 hardglycolate)₂ and 24 h and 24 h and 24 h and 24 h 4 MoMoO₂(1,2-propanediolate)₂ <05:00  <05:00  <05:00   5:07 hard 5 MoMoO₂(1,2-octanediolate)₂  2:30  3:00  3:00 3 h 30 hard 6 MoMoO₂(2,3-butanediolate)₂ 03:00  3:00  3:30 03:40 hardThe results of the RTV2 test (ethyl silicate crosslinker) are given intable II below:

TABLE II Ethyl silicate RTV2 tests Time when Time to end Tack-freeCrosslinking stirring stops of flowability time time Hard/soft Test No.Metal Catalyst (h:min) (h:min) (h:min) (h:min) after 24 h Comparative SnTegokat225 00:20 00:30 00:42 00:42 hard example 1 Mo MoO₂(ethyleneglycolate)₂ 00:30 00:30 00:45 00:45 hard 2 Mo MoO₂(1,2-propanediolate)₂00:48 02:00 02:00 02:00 hard 3 Mo MoO₂(2,3-butanediolate)₂ 00:10 00:15 0:15 00:25 hard 4 Mo [MoOH(pinanediolate)₂]₂O 04:00 04:25 04:25 04:25hardThe results of the RTV2 test (“advanced silicate” crosslinker) are givenin table III below:

TABLE III “Advanced” ethyl silicate RTV2 tests Time when Time to endTack-free Crosslinking stirring stops of flowability time time Hard/softTest No. Metal Catalyst (h:min) (h:min) (h:min) (h:min) after 24 hComparative Sn Tegokat225 00:24 00:29 00:32 00:36 soft hard example00:50 hard 1 Bi Bi(ethylene glycolate 00:02 00:10 00:25 00:25 hardmonoallyl ether)₃ 2 Mo MoO₂(1,3-propanediolate) 05:20 05:20 05:25 09:00soft soft 3 Mo MoO₂(ethylene glycolate)₂ 00:43 00:47 00:47 00:47 hard 4Mo MoO₂(1,2-propanediolate)₂ 00:43 00:54 00:54 00:54 hard 5 MoMoO₂(1,2-octanediolate)₂ 00:15 00:15 00:15 00:20 hard 6 MoMoO₂(2,3-butanediolate)₂  0:40  0:50 00:50 1:00 to 1:40 hard 7 MoMoO₂(meso-2,3- 00:25 00:35 00:35 01:00 soft very hard butanediolate)₂ 8Mo (MoOH(2,3-butanediolate)₂)₂O 04:30 04:30 05:00 05:20 very hard 9 MoMoO₂(pinacol)₂ 04:30 04:30 04:30 04:30 very hard

Example 3 Paste Test for RTV1 and RTV2 Compositions

Subsequently, certain catalysts were also tested in closer systems knownas “pastes”.

In RTV1 compositions, the paste used was prepared as follows: added,with stirring, to a mixture of 3464 g of an α,ω-dihydroxylated oil witha viscosity of 20 000 centipoise containing 0.066% of OH, and of 120 gof vinyltrimethoxysilane were 16 g of a 2 wt % solution of lithiumhydroxide in methanol, then, after 5 min, 400 g of AE55 fumed silicawere added. The mixture was devolatilized under vacuum then stored in amoisture-free environment.

For each test, the catalyst tested was mixed with 50 g of this paste,then the catalytic potential was evaluated in 3 ways:

-   -   the skin-over time (SOT), time at the end of which surface        crosslinking is observed, on a 2 mm film;    -   the persistence of a tacky feel at 48 h;    -   the hardness (Shore A hardness) of a 6 mm thick bead under        controlled conditions (23° C. and 50% relative humidity) and        over increasing times (2, 3, 7 and 14 days). The high        temperature stability was also evaluated by hardness        measurements carried out on the bead after 7 days at room        temperature followed by 7 days at 100° C.    -   NB: The Shore hardness was measured on a 6 mm bead. In the table        of results the symbol “>” corresponds to the hardness values        measured on the upper part of the bead and the symbol “<”        corresponds to the hardness values measured on the lower part of        the bead that is less exposed to the ambient air than the upper        part.

Various catalysts according to the invention were tested.

By way of comparison, as above, the following was also tested:

a tin-based catalyst: dibutyltin dilaurate (DBTDL);

The results are given in table III below.

TABLE III RTV1 paste test Shore A hardness over 6 mm SOT Tacky 7 d RT +% by stick feel 2 d 3 d 4 d 7 d 14 d 7 d 100° C. Product weight min at48 h > < > < > < > < > < > < Comparative example 0.9 10 no 32 22 32 29DBTDL MoO₂(butanediolate)₂ 1.6 60 no gel gel gel 14 5 24 20 33 21 at 50%in isopropanol

In RTV2 compositions, the tests were carried out directly on a mixtureof a viscous dihydroxylated oil (48V14000) and of advanced silicatecrosslinker (1 g per 22.5 g of oil) to which the catalyst was added andmixed therewith. Firstly, the pot-life was measured (time at the end ofwhich the viscosity of the mixture prevents it from being used), then,starting from another mixture, a slug with a thickness of 6 mm was castfor the measurements of hardness over time.

NB: The Shore hardness was measured on the 6 mm slug. In the table ofresults the symbol “>” corresponds to the hardness values measured onthe upper part of the slug and the symbol “<” corresponds to thehardness values measured on the lower part of the slug that is lessexposed to the ambient air than the upper part.By way of comparison, as above, the following was also tested:

a tin-based catalyst: dimethyltin dineodecanoate (UL28).

The results are given in table IV below.

TABLE IV RTV2 paste tests Shore A hardness over 6 mm % by Pot-life 1 d 4d 21 d 35 d Catalyst Solvent mol eq weight (min) > < > < > < > < UL28 /1 1.4 23 24 19 25 25 23 23 22 22 MoO₂(1,2-propanediolate)₂ crosslinker 10.8 — 13 0 15 14 17 16 17 17 MoO₂(1,2-octanediolate)₂ crosslinker 1 1.211 8 0 10 8 11 12 13 14 MoO₂(2,3-butanediolate)₂ crosslinker 1 0.9 60 120 23 0 24 26 24 27

1. An organopolysiloxane composition, comprising: a silicone base Bcapable of curing via polycondensation reaction into a siliconeelastomer, said silicone base comprising: at least onepolyorganosiloxane oil C capable of crosslinking via polycondensationinto an elastomer; optionally at least one crosslinking agent D;optionally at least one adhesion promoter E; and optionally at least onesiliceous, organic and/or non-siliceous mineral filler F; and acatalytically effective amount of at least one polycondensation catalystwhich is a metal complex or salt A of formula (1) below:[M(L¹)_(r1)(L²)_(r2)(Y)_(x)]  (1) in which: r1≧1, r2≧0 and x≧0; thesymbol M represents a metal selected from the group constituted by:cerium, bismuth and molybdenum; the symbol L¹ represents a ligand whichis an alcoholate anion and when r1≧2, the symbols L¹ are identical ordifferent; the symbol L² represents an anionic ligand which is differentfrom L¹ and when r2≧2, the symbols L² are identical or different; andthe symbol Y represents a neutral ligand and when x≧2, the symbols Y areidentical or different.
 2. The organopolysiloxane composition as claimedin claim 1, wherein the polycondensation catalyst is a metal complex orsalt A of formula (1′) below:[M(L¹)_(r1)(L²)_(r2)]  (1′) in which: r1≧1 and r2≧0; the symbol Mrepresents a metal selected from the group constituted by: cerium,bismuth and molybdenum; the symbol L¹ represents a ligand which is analcoholate anion and when r1≧2, the symbols L¹ are identical ordifferent; and the symbol L² represents an anionic ligand which isdifferent from L¹ and when r2≧2, the symbols L² are identical ordifferent.
 3. The organopolysiloxane composition as claimed in claim 1,wherein said composition comprises, on the one hand, a silicone base Bcapable of curing via polycondensation reaction into a siliconeelastomer and, on the other hand, a catalytically effective amount of atleast one polycondensation catalyst which is a metal complex or salt Afrom the group constituted by the complexes of formulae (2) to (4)below:[Ce(L¹)_(r3)(L²)_(r4)];where r3≧1 and r4≧0 and r3+r4=3;  (2)[Mo(L¹)_(r5)(L²)_(r6)];where r5≧1 and r6≧0 and r5+r6=6;  (3)[Bi(L¹)_(r7)(L²)_(r8)];where r7≧1 and r8≧0 and r7+r8=3;  (4) in which:the symbol L¹ represents a ligand which is an alcoholate anion and whenthe number of ligands L¹≧2, the symbols L¹ possibly being identical ordifferent; and the symbol L² represents an anionic ligand which isdifferent from L¹ and when the number of ligands L²≧2, the symbols L²possibly being identical or different.
 4. The organopolysiloxanecomposition as claimed in claim 1, wherein the symbol L¹ represents aligand which is an alcoholate anion chosen from the group constituted bythe alcoholate anions derived from the following alcohols: methanol,ethanol, propanol, isopropanol, n-butanol, cyclopentanol, cycloheptanol,cyclohexanol, s-butanol, t-butanol, pentanol, hexanol, octanol, decanol,isopropyl alcohol, allyl alcohol, diols such as, for example, ethyleneglycol, 1,2-propanediol, pinanediol, 1,3-propanediol and 1,2-octanediol,1,2-cyclohexanediol, 2,3-butanediol and ethylene glycol.
 5. Theorganopolysiloxane composition as claimed in claim 1, wherein saidcomposition comprises, on the one hand, a silicone base B capable ofcuring via polycondensation reaction into a silicone elastomer and, onthe other hand, a catalytically effective amount of at least onepolycondensation catalyst which is a metal complex or salt A chosen fromthe group constituted by the complexes (5) to (14) below:[Ce(OiPr)₄]where(OiPr)=the isopropylate anion;  (5)[Mo(O₂)(2,3-butanediolate)₂];  (7)[Mo(O₂)(ethylene glycolate)₂];  (8)[Mo(O₂)(1,2-propanediolate)₂];  (9)[Mo(OH)(pinanediolate)₂];  (10)[Mo(O₂)(1,3-propanediolate)₂];  (11)[Mo(O₂)(meso-2,3-butanediolate)₂];  (12)[Mo(O₂)(1,2-octanediolate)₂];and  (13)[Bi(monoallyl ethylene glycolate)₃].  (14)
 6. The organopolysiloxanecomposition as claimed claim 1, wherein L² is an anionic ligand selectedfrom the group constituted by the following anions: fluoro (F⁻), chloro(Cl⁻), triiodo (1⁻) (I₃)⁻, difluorochlorato (1⁻) [ClF₂]⁻,hexafluoroiodato (1⁻) [IF₆]⁻, oxochlorato (1⁻) (CIO)⁻, dioxochlorato(1⁻) (CIO₂)⁻, trioxochlorato (1⁻) (CIO₃)⁻, tetraoxochlorato (1⁻)(CIO₄)⁻, hydroxo (OH)⁻, mercapto (SH)⁻, selanido (SeH)⁻, hyperoxo (O₂)⁻,ozonido (O₃)⁻, hydroxo (OH⁻), hydrodisulfido (HS₂)⁻, methoxo (CH₃O)⁻,ethoxo (C₂H₅O)⁻, propoxido (C₃H₇O)⁻, methylthio (CH₃S)⁻, ethanethiolato(C₂H₅S)⁻, 2-chloroethanolato (C₂H₄CIO)⁻, phenoxido (C₆H₅O)⁻, phenylthio(C₆H₅S)⁻, 4-nitrophenolato [C₆H₄(NO₂)O]⁻, formato (HCO₂)⁻, acetato(CH₃CO₂)⁻, propionato (CH₃CH₂CO₂)⁻, nitrido (N₃)⁻, cyano (CN)⁻, cyanato(NCO)⁻, thiocyanato (NCS)⁻, selenocyanato (NCSe)⁻, amido (NH₂)⁻,phosphino (PH₂)⁻, chloroazanido (ClHN)⁻, dichloroazanido (Cl₂N)⁻,[methanaminato (1⁻)] (CH₃NH)⁻, diazenido (HN═N)⁻, diazanido (H₂N—NH)⁻,diphosphenido (HP═P)⁻, phosphonito (H₂PO)⁻, phosphinato (H₂PO₂)⁻,carboxylato, enolato, amides, alkylato and arylato.
 7. Theorganopolysiloxane composition as claimed in claim 1, wherein L² is ananionic ligand selected from the group constituted by the followinganions: acetate, propionate, butyrate, isobutyrate, diethylacetate,benzoate, 2-ethylhexanoate, stearate, methoxide, ethoxide, isopropoxide,tert-butoxide, tert-pentoxide, 8-hydroxyquinolinate, naphthenate,tropolonate and the oxido O²⁻ anion.
 8. A two-component system that is aprecursor of the organopolysiloxane composition as defined as claimed inclaim 1 and that can be vulcanized to a silicone elastomer viapolycondensation reactions wherein said system is in two separate partsP1 and P2 intended to be mixed in order to form said composition, andone wherein of said parts comprises the metal complex or salt A as acatalyst for the polycondensation reaction of organopolysiloxanes andthe crosslinking agent D and the other part is free of the catalyst andcrosslinking agent D and comprises: per 100 parts by weight of thepolyorganosiloxane oil(s) C capable of crosslinking via polycondensationinto an elastomer; and from 0.001 to 10 part(s) by weight of water.
 9. Asingle-component organopolysiloxane composition that is stable duringstorage in the absence of moisture and that crosslinks, in the presenceof water, into an elastomer, wherein said composition comprises: atleast one crosslinkable linear polyorganopolysiloxane that hasfunctionalized ends of alkoxy, oxime, acyl and/or enoxy type, preferablyalkoxy type; a filler; and a catalyst of a polycondensation reactionwhich is the metal complex or salt A as defined as claimed claim
 1. 10.An elastomer obtained by crosslinking and curing the composition asclaimed claim
 1. 11. A metal complex or salt A as claimed in claim 1 asa catalyst a polycondensation reaction of organopolysiloxanes.
 12. Acatalyst for the polycondensation reaction of organopolysiloxanes,comprising a compound of formulae (5) to (14) below:[Ce(OiPr)₄]where(OiPr)=the isopropylate anion;  (5)[Mo(O₂)(2,3-butanediolate)₂];  (7)[Mo(O₂)(ethylene glycolate)₂];  (8)[Mo(O₂)(1,2-propanediolate)₂];  (9)[Mo(OH)(pinanediolate)₂];  (10)[Mo(O₂)(1,3-propanediolate)₂];  (11)[Mo(O₂)(meso-2,3-butanediolate)₂];  (12)[Mo(O₂)(1,2-octanediolate)₂];and  (13)[Bi(monoallyl ethylene glycolate)₃].  (14)
 13. The compounds of thefollowing formulae:[Mo(OH)(pinanediolate)₂];  (10)[Bi(monoallyl ethylene glycolate)₃].  (14)